Time delay circuits



April 14, 1953 W. B. BRUENE 2,635,213

TIME DELAY CIRCUITS Filed July 10, 1950 '92 QL 'f' INVENTOR. f W mam B. Blu/m:

10 zo so 40 so ao BY 7744: OFF /ly .Sram/08 M 2%'74 Patented Apr. 14, 1953 TIME DELAY CIRCUITS Warren B. Bruene, Cedar Rapids, Iowa, assignor to Collins Radio Company,` Cedar Rapids, Iowa,

o, corporation of Iowa Application July 10, 1950, Serial NO. 172,990 i olzims. (Cl. :mz-97) This invention relates in general to time delay circuits end. in particular to apparetus which will rccover from an inteifruption of powet` in a time depending upon the length of the interruption.

In the operation of many electronic devices it is desir'able to allow' a portion' of the equipment to be turned on before other equipment. For example, when :iy large radio transmitter is put onthe sir, it is desirsble to allow the filsments to' heat up to an emission temperature before applying voltage to the rectifier tubes. At times the power to the ti'ansmitter mety be interrupted either permanently or momenta-rily. In the case of the pc'rmanent interruption, the filamen't must once again be hosted prior to the application of plate voltage, but ii the interifuption is a momentory one whei'ein the heater nas remained at an emission temperature during the brief power-off interva'l, it is desirable to have the plate Voltage turned on again es soon as practicable.

It is an object of this ihvention therefore to provide a control means which does not turn off the plate voltage during short interruptions of powei'.

Another object of this inventlon is to provide means for turning on the plate voltage of an electronic device at a; time related to the length of the power-off period.V

Another object of this invention is to provide a delay apparetus which actuates' a Circuit after en interruption has occurred at atime proportional to the intenfuption per'iod.

Further objects, features and advantges of this invention will become apparent from the following description and claims when read. in view of the drawings, in which:

Figure `1 is the wifing diagram of the time delay cicuit of this invention;

Figure 2 is a. wii'ing diagram of a modification of the invention; and,

Figure 3 is a plot of intei'rupton time versus delay time.

Figura 1 illustiates a) trode tube [0 which has a plate H, control grid l2, cathode 13, and filai-ent heater Mc The filament heater M may he connected to a suitable filelrnent voltage supplz:7 received. from a transformer IE which is connecte'd to a suitable power source through the leads i and I'I. The cathode i3 of tube li! is connected to a rela coil 2|' in parallel with av condenser Cz. The opposite sides of the relay 2| 'and the condenser Cz' sie connected to the lead 9. Also connected to the cathode i3 is a, resistoi' R1 'which is in series with a condenser C1 that has its opposite side connected to the lead 19. A grid 2 leak resistor Rz is connected between the condenser C1 end the grid 42. The plate H is con-v nected to e lead 13. A high voltage is applied between leads I 8 and Is. The relay 2| has a movable'arinature 22. The ei'mature 22 is connected to a lead 23 and is movable to engage a contact 2| when in its closed position. Actuation of the armatura 22 makes electrical contact between the contact 24 and the lead 23.

In Figura l the contact 24 is shown connected to the power supply of o pair of vapor diode rectifiei's 27 and 28 which have their filaments 29 and 34 connected to a second winding of transformer IE. The leads 23 and 30 are connected to a power source. Thus the filaments of the i'ectifiers will he heeted, prior to the application of voltage to the plates 32 and Thiswill assure satisfactory operation of the i'ectifiers and will prevent sputtei'ing of the cathode. The output of the rectiei's might be supplied, for example, to the plate Circuit of a transmitter connected to terminals 34 and 3B.

In operation, when power is supplied to the leads IB, Il, l, iS, 23 and 30, simultaneously,

' the i'elay 2| will be actuated a predetermined time after the power is turned on. When the filament power supplied to leads 16 and IT is connected, no current flows through the tube IO until the filament 14 has reached an emission temperature. This causes the cethode |3 to emit electrons. Then current will flow through the tube IO upon the' positive half cycles, if alternating current is applied between the leads l8 and |9. II direct current is applied between these leads, current-s will now all the time after the cathode commences to emit electrcns. This plate current passes through the rela-y 2! connected in parallel with the condenser Cz. The voltage drop across the relay zl and the condenser Cz causes the condcnsei` C1 to start cherging through resis'tance R1. 'The' grid voltage is determined by the difference in charge between C1 and Cz so the rate at which the cathode voltage increases is determined by the time constant R1 and Ci and also the amplifi'cetion factor of the tube. The charging current of condenser Ci is equal to the gi'id-cathode voltage divided by' R1 which ls rather small end neai'ly Constant over most of the tlming cycle. This circuit allows relatively long delalys to he obtained with reasonable values Of R1 and C1.

When the voltage across the relay 2| has built up suillciently, it will close the armatura 22, thus connecting the lead 23 to contact 24. The

cathode voltage continues to build up to an equilibrium point and remains there.

If the power supply to leads [8 and IS and IB and I 1, respectively, is removed or lost for a short period of time, the armature 22 will not disconnect the contact 24 from lead 23 because the large capacitor C2 across the relay will keep current fiowin'g in the relay until the voltage drops to approximately one-half of its operating value. As the relay voltage drops, condenser C1 starts discharging through resistances R1 and Rz through the tube. When the tube cathode cools down suficiently, the tube discharge through R2 Will not be large and then the major discharge' of C1 will be through R1. The discharge time will be several times less than the charging time,

and if power is reapplied before the discharge is complete, but the relay armature 22 has opened,

it will close with less delay than it would Vhave` had the circuit been completely discharged.

Thus, a momentary loss of power may cause no' delay when power is resumed, or only al short delay, depending upon the amount of time power is off and value of time' delay circuit components.

The: values of the components in this `circuit might be, for example.

R1, 1.2 megoh'ms.

R2, 1.2 megohms.

Ci, lmicrofarad.

Cz, 20 microfaradselectrolytic.

Direct current resistance of relay 2 l, 15,500 ohms.

- Relay 2! is actuated at 82 volts and disengages at 50 volts. With the above components and 230 Volts A. C. applied between leads lg and IS, twenty-nine seconds elapsed after closing of the circuit'` before the relay was actuated. This is ample time for allowing the filaments `of the rectifierl tubes to heat.

-Figure 3 is a plot of delay time" versus 'time off -where delay time is the time to operate relay 2| when power is turned on and time-off is -thelength of the interruption of power. Thus if the tube Ill has reached equilibrium with the relay 2! closed and power is interrupted for ten seconds, the relay would be actuated 18 seconds after power was re-applied. If the time off'? is equal to one second or less, however, there would, be no delay because the relay would stay closed for this short time.

Figure 2 illustrates a ymodification of this inyention wher'ein a diode 3? is connected in parallel with a resistor-R3 between the cathode I 3 and resistor R1. This diode makes it possible to charge C1 through the resistor R1, but prevents C1'from disoharging through R1 alone. Resistor Rz'allows a slow rate of discharge of the condenser C1. It is seen that this invention provides means for controlling the application of high power to apparatus after there has been a momentary interruption of power. There are many uses which might be made of this invention and the diode rectifiers of a transmitter have been used as illustrative examples only. Although this invention has been described with respect to particular embodiments thereof, it is not to be so limited as changes and modifications may be made therein which are within the full intended scope of the invention as defined by the appended claims.

I claim: 1. Control means for connecting a power supply to a plate circuit a predetermined time after the application ,of power to a portion of thecircuit comprising, a first electron tube, a filament heater of said first electron tube connected to said power supply, afirst resistor connected to the cathode of said first electron tube, a first condenser connected in series with said first resistor and to one side of said power supply, a second condenser, an electromagnetic relay connected in parallel with said second condenser and the parallel combination connected between the cathode of the first electron tube and the one side ofsaid power supply, the plate of said first electron tube connected to the other side of said power supply, a controlled tube with its filament connected to the power supply, the plate of said controlled tube connected to said power supply,

and a two position switch in the plate circuit of said controlled tube and connected to the electromagnetic relay.

- 2.v Means for controlling the application of high voltage from a power supply between plate and cathode of a controlled tube comprising, a first electron tube, a high voltage power supply,a transformer with its primary connected to high Voltage supply, a heater for said first electron tubeconnected to the secondary of said transformer, the plate of said first electron tube connected to one side of said power supply, a firstresistor connected to the cathode of said electron tube, a first condenser connected in series with the first resistor and the other side of said high power supply, an electromagnetic relay, a second condenser connected in parallel with said electromagnetic relay, said second condenser and relay connected between the cathode of said first electron tube and the other side of said power supply, heaters for said controlled tube connected to the secondary of said transformer, the plate-of said controlled tube connected to the power supply, and the armatura of said relay connected in series with the plate of said controlled tube to open and close the plate circuit of the controlled tube in response to operation of said relay.

3. Means for controlling the power to a pairof diode rectifiers comprising, a first electron tube, a transformer connected to a power supply, the filament heater of said first electron tube connected to the secondary of said transformer, the plate of said first electron tube connected to one side of the power supply, a first resistor, a first condenser connected in series with said first resistor between the'cathode of said first electron tube and the other side of the power supply,- aj second resistor connected between the control'grid of said first electron tube and said first condenser, a second condenser, an electromagnetic relay connected in parallel With said second condenser, the cathode of said first electron tube connected to one side of said second condenser, the other side of said power supply connected to the opposite side of said second condenser, the filaments of said diode rectifiers connected to the secondary of said transformer, a high voltage supply connected to the plates of said diode rectifiers, and said relay controlling the application of power from said high voltage supply tol the plates of said diode rectifiers.

4. Means for actuating an electroma'gnetic relay so that its closing and opening times are functions of the time it has been open comprising, a firstl electron tube, a heater of said first electron tube connected to a power supply, the plate of said first electron tube connected to one side of the power supply, a first condenser connected tethe other. side of the power supply, a

5 first resistor connected to the other side of said first condenser, a rectifier tube with its plate connected to the cathode of the first electron tube and its cathode connected to the first re'- sistor, a second resstor connected between the control grid of the first eiectron tube and the first condenser, a, third resistor connected in parailel with said rectifier tube, a second condenser, and the electromagnetic relay connected in parallel With said second condenser and one side of the relay connected to one side of the power supply and the other side connected to the cathode of the first electron tube.

WARREN B. BRUENE.

References Cited in the file o! this patent UNITED STATES PATENTS Number Name Date Huber July 7, 1936 Lazzarini Mar. 16, 1937 Sledd Dec. 12, 1939 Brown Oct. 6, 1942 'Kingsmill June 10, 1947 Haungs May 25, 1948 Brown Apr. 12, 1949 Faulk June 21, 1949 Davids Sept. 27, 1949 

